The present invention relates to the shielding method and structure for a multicore shielded wire for electrically connecting a shielding cover of the multicore shielded wire and a grounding wire.
A related shield processing structure is disclosed in Japanese Patent Publication No. 11-135167A as shown in FIGS. 8 and 9.
In the branching structure shown in these figures, a braided wire 120d of a shielded wire 120 is electrically connected to a conductive wire 123a of a grounding wire 123 by an ultrasonic horn 125 through a pair of resin members 121 and 122.
In other words, the shielded wire 120 is constituted by one shielding core 120c having a core 120a covered with an insulating inner sheath 120b, a conductive braided wire 120d for covering the outer periphery of the shielding core 120c, and an insulating outer sheath 120e for further covering the outer periphery of the braided wire 120d. A pair of resin members 121 and 122 have concave portions 121b and 122b for forming a hole corresponding to the outer sectional shape of the shielded wire 120 with mutual bonding faces 121a and 122a butted against each other, respectively. The grounding wire 123 is constituted by the conductive wire 123a and an insulating outer sheath 123b for covering an outer periphery thereof. The ultrasonic horn 125 is constituted by a lower support base (not shown) provided in a lower part and an ultrasonic horn body 125a provided in an upper part.
Next, a branching procedure will be described. The lower resin member 122 is provided on the lower support base (not shown) of the ultrasonic horn 125, the shielded wire 120 is mounted thereabove, one end of the grounding wire 123 is mounted thereon, and furthermore, the upper resin member 121 is put thereabove. Thus, the shielded wire 120 is provided in the concave portions 121b and 122b of the resin members 121 and 122, and the grounding wire 123 is provided between the shielded wire 120 and the upper resin member 121.
In this state, a vibration is applied by the ultrasonic horn 125 while applying compression force between the resin members 121 and 122. Consequently, the insulating outer sheath 120e of the shielded wire 120 and the insulating outer sheath 123b of the grounding wire 123 are fused and scattered by the internal heat generation of a vibration energy so that the conductive wire 123a of the grounding wire 123 and the braided wire 120d of the shielded wire 120 come in electrical contact with each other. Moreover, each of the contact portions of the bonding faces 121a and 122a of the resin members 121 and 122, the contact portion of the internal peripheral faces of the concave portions 121b and 122b of the resin members 121 and 122, the insulating outer sheath 120e of the shielded wire 120, the contact portion of the insulating resin 123b of the grounding wire 123, and the resin members 121 and 122 are fused by the heat generation of the vibration energy and the fused portions are solidified after the ultrasonic vibration is completely applied. Consequently, the resin members 121 and 122, the shielded wire 120 and the grounding wire 123 are fixed to each other.
According to the branch processing, it is not necessary to peel the insulating outer sheaths 120e and 123b of the shielded wire 120 and the grounding wire 123, and the lower resin member 122, the shielded wire 120, the grounding wire 123 and the upper resin member 121 are simply assembled in this order to give the ultrasonic vibration. Consequently, the number of steps is decreased, and complicated manual work is not required and automation can also be achieved.
In the branching structure, the single core type shielded wire 120 can be properly shielded. However, if the same structure is applied to a multicore type shielded wire having a different internal configuration, the following drawbacks would occur.
More specifically, a multicore shielded wire has such a structure that a plurality of shielded core wires are accommodated with a clearance in the internal space of an insulating outer sheath and a braided wire. For this reason, the degree of close contact and the arrangement relationship between the braided wire and the shielded core wires are indefinite with an interposition between the resin members 121 and 122. In some cases in which the degree of close contact is excessive, the insulating inner sheath of the shielded core wire is broken or cut upon receipt of the transmission of great vibration energy. Consequently, the grounding wire or the shielding cover comes in contact with the core to cause a short circuit, and furthermore, the strength of the multicore shielded wire is reduced.
In order to eliminate such a drawback, it can be proposed that the vibration energy to be applied by the ultrasonic vibration Is reduced. However, in such a condition, a bonding strength based on the fusion and solidification between the resin members 121 and 122 is accordingly reduced.
It is therefore an object of the invention to provide a structure and a method for shielding a multicore shielded wire in which a short circuit can be prevented from being caused by the contact of a grounding wire or a shielding cover with a core wire so that the strength of the multicore shielded wire can be prevented from being reduced.
In order to achieve the above object, according to the present invention, there is provided a multicore shielded wire, comprising:
a plurality of shielded core wires, each having a first diameter;
a conductive cover member, which covers the shielded core wires;
a first insulating sheath, which covers the conductive cover member; and
a pair of resin members, each formed with a groove having a semi-ellipsoidal shape and thermally integrated with each other for forming an ellipsoidal through hole while accommodating the first insulating sheath therein,
wherein a major axis length of a cross section of the ellipsoidal through hole is substantially identical with a length obtained by adding each first diameter, twice a thickness of the conductive cover member and twice a thickness of the first insulating sheath; and
wherein a minor axis length of a cross section of the ellipsoidal through hole is substantially identical with a length obtained by adding the first diameter, twice the thickness of the conductive cover member and twice the thickness of the first insulating sheath.
Preferably, the multicore shielded wire further comprises a branch wire, in which a conductive core wire is covered with a second insulating sheath, the branch wire sandwiched between the first insulating sheath and one of the resin members. A part of the first insulating sheath and a part of the second insulating sheath are thermally fused so that the conductive cover member and the conductive core wire are electrically connected.
In order to attain the same advantages, according to the present invention, there is also provided a multicore shielded wire, comprising:
a plurality of shielded core wires, each having a first diameter;
at least one drain wire, having a second diameter which is smaller than the first diameter;
a conductive cover member, which covers the shielded core wires and the drain wire;
a first insulating sheath, which covers the conductive cover member, and
a pair of resin members, each formed with a groove having a semi-ellipsoidal shape and thermally integrated with each other for forming an ellipsoidal through hole while accommodating the first insulating sheath therein,
wherein a major axis length of a cross section of the ellipsoidal through hole is substantially identical with a length obtained by adding each first diameter, the second diameter, twice a thickness of the conductive cover member and twice a thickness of the first insulating sheath; and
wherein a minor axis length of a cross section of the ellipsoidal through hole is substantially identical with a length obtained by adding the first diameter, twice the thickness of the conductive cover member and twice the thickness of the first insulating sheath.
Preferably, the multicore shielded wire further comprises a branch wire, in which a conductive core wire is covered with a second insulating sheath, the branch wire sandwiched between the first insulating sheath and one of the resin members. A part of the first insulating sheath and a part of the second insulating sheath are thermally fused so that the conductive cover member and the conductive core wire are electrically connected.
In order to attain the same advantages, according to the present invention, there is also provided a method of shielding a multicore shielded wire, comprising the steps of:
providing a plurality of shielded core wires, each having a first diameter;
covering the shielded core wires with a conductive cover member;
covering the conductive cover member with a first insulating sheath
providing a branch wire, in which a conductive core wire is covered with a second insulating sheath;
pressurizing the first insulating sheath so as to have an ellipsoidal cross section in which the shielded core wires are aligned in a major axis direction of the ellipsoidal cross section;
providing a pair of resin members, each formed with a groove having a semi-ellipsoidal shape;
sandwiching the first insulating sheath and the branch wire between the resin members, such that the first insulating sheath is accommodated within an ellipsoidal through hole formed by the grooves and such that the branch wire is placed between the first insulating sheath and one of the resin members;
applying an ultrasonic vibration such that the resin members are integrated with each other, while thermally fusing a part of the first insulating sheath and a part of the second insulating sheath so that the conductive cover member and the conductive core wire are electrically connected,
wherein a major axis length of a cross section of the ellipsoidal through hole after the ultrasonic vibration applying step is substantially identical with a length obtained by adding each first diameter, twice a thickness of the conductive cover member and twice a thickness of the first insulating sheath; and
wherein a minor axis length of a cross section of the ellipsoidal through hole after the ultrasonic vibration applying step is substantially identical with a length obtained by adding the first diameter, twice the thickness of the conductive cover member and twice the thickness of the first insulating sheath.
In order to attain the same advantages, according to the present invention, there is also provided a method of shielding a multicore shielded wire, comprising the steps of:
providing a plurality of shielded core wires, each having a first diameter;
providing at least one drain wire, having a second diameter which is smaller than the first diameter;
covering the shielded core wires and the drain wire with a conductive cover member;
covering the conductive cover member with a first insulating sheath;
providing a branch wire, in which a conductive core wire is covered with a second insulating sheath;
pressurizing the first insulating sheath so as to have an ellipsoidal cross section in which the shielded core wires and the drain wire are aligned in a major axis direction of the ellipsoidal cross section;
providing a pair of resin members, each formed with a groove having a semi-ellipsoidal shape;
sandwiching the first insulating sheath and the branch wire between the resin members, such that the first insulating sheath is accommodated within an ellipsoidal through hole formed by the grooves and such that the branch wire is placed between the first insulating sheath and one of the resin members;
applying an ultrasonic vibration such that the resin members are integrated with each other, while thermally fusing a part of the first insulating sheath and a part of the second insulating sheath so that the conductive cover member and the conductive core wire are electrically connected,
wherein a major axis length of a cross section of the ellipsoidal through hole after the ultrasonic vibration applying step is substantially identical with a length obtained by adding each first diameter, each second diameter, twice a thickness of the conductive cover member and twice a thickness of the first insulating sheath; and
wherein a minor axis length of a cross section of the ellipsoidal through hole after the ultrasonic vibration applying step is substantially identical with a length obtained by adding the first diameter, twice the thickness of the conductive cover member and twice the thickness of the first insulating sheath.
In the above configurations, the conductive cover member deforms scarcely even if the pressing force is applied to the multicore shielded wire at the time of sandwiching the multicore shielded wire between the pair of the resin members, the branch wire and the conductive cover member before the fusing process caused by the ultrasonic vibration are disposed at the constant positions, and the plurality of the shielded core wires can scarcely move. Thus, the shielded core wires are not displaced even when the pressure and the ultrasonic vibration is applied. Thus, the insulating sheath of the shielded core wires are not broken or out due to the heat generated by the ultrasonic vibration.